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Synthesis and characterisation of novel metal pyrophosphates

Baker, Annabelle R. (2014)
Ph.D. thesis, University of Birmingham.

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Abstract

This thesis describes the synthesis, properties and structural characterisation of Mg\(^2\)\(^+\), Mn\(^2\)\(^+\)and Ti\(^4\)\(^+\) pyrophosphates and Li and V substituted analogues.
α and β polymorphs of MgH\(_2\)P\(_2\)O\(_7\), were isolated by a novel acid melt synthetic route. Both polymorphs crystallised in monoclinic space groups, with α-MgH\(_2\)P\(_2\)O\(_7\) isostructural with NiH\(_2\)P\(_2\)O\(_7\) and β-MgH\(_2\)P\(_2\)O\(_7\) isostructural with CaH\(_2\)P\(_2\)O\(_7\). Rietveld refinements of NPD data gave excellent fits to both structural models. MgLi\(_0\)\(_.\)\(_8\)H\(_1\)\(_.\)\(_2\)P\(_2\)O\(_7\)was also isolated with Rietveld refinement suggesting two similar possible structural models.
MnH\(_2\)P\(_2\)O\(_7\), a structural polymorph of β-MgH\(_2\)P\(_2\)O\(_7\) was also synthesised via a similar route. Magnetic analysis revealed MnH\(_2\)P\(_2\)O\(_7\) to be paramagnetic, with a small antiferromagnetic component. Incorporation of Li was again achieved via the addition of lithium carbonate during synthesis. Rietveld refinement of NPD data suggests a similar structure to that of MnH\(_2\)P\(_2\)O\(_7\) and a composition of MnLi\(_0\)\(_.\)\(_5\)H\(_1\)\(_.\)\(_5\)P\(_2\)O\(_7\).
A metastable polymorph of TiP2O7 has been successfully synthesised at low temperature and adopts a structure similar to the ideal cubic structure. Incorporation of vanadium resulted in an expansion of the unit cell. Both phases undergo a phase transition above 275°C to the ideal cubic structure. Addition of vanadium results in an unusual uniform spherical morphology unseen in parent phase.

Type of Work:Ph.D. thesis.
Supervisor(s):Wright, Adrian
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Subjects:QD Chemistry
Institution:University of Birmingham
ID Code:5524
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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